13presure solid liquids and gases

Solid, Liquids, and Gases
Their properties and changes

The three states of matter.

Silberberg, Principles of Chemistry

Gases
• Because gases have so much space between
the particles they have properties that are
dependent on one another.

Gas Variables
• Volume (V) - mL, L, kL…
• Temperature (T) – oC measured in lab but K
(kelvin) for calculations
• Number of particles (n) – moles
• Pressure (P) – mmHg, psi… more to come

Pressure
• Force per unit area

A mercury barometer
Figure 5.3

Silberberg, Principles of Chemistry

Table 5.1 Common Units of Pressure
Unit

Atmospheric Pressure

Scientific Field

pascal(Pa);
kilopascal(kPa)

1.01325x105Pa;
101.325 kPa

SI unit; physics, chemistry

atmosphere(atm)

1 atm*

chemistry

millimeters of
mercury(Hg)

760 mm Hg*

chemistry, medicine, biology

torr

760 torr*

chemistry

14.7lb/in2

engineering

1.01325 bar

meteorology, chemistry,
physics

pounds per square inch
(psi or lb/in2)
bar

*This is an exact quantity; in calculations, we use as many significant figures as necessary.
Silberberg, Principles of Chemistry

Gas Variable Relationships
• To investigate the relationship between 2 gas
variables we need to hold the other 2
constant.

• Constant P - same # of collisions/unit area
• Constant V - rigid container
• Constant T – thermostat control
• Constant n – keep container sealed

The Relationship Between
Pressure and Volume

Silberberg, Principles of Chemistry

The relationship between the volume and pressure of a gas.

PV
1 1 = PV
2 2
Boyle’s Law

Silberberg, Principles of Chemistry

A molecular description the relationship

between temperature and volume.

The relationship between the
volume and temperature of a gas.

Charles’s Law

V2
T2
=
V1
T1

The relationship between pressure and
temperature
•As temperature
increases, gas particles
move faster and make
more collisions. As a
result the pressure in the

container increases.
•For an aerosol can the
pressure may be so great
that the seam on the can
may give way in an
explosion.

An experiment to study the relationship between the volume and
amount of a gas.

V  n or V = constant x n
The more gas particles you have the more collisions
occur. To keep the pressure the same, the volume has
to increase so there is more room for the particles.
This is why balloons expand when you blow air into
them.

Solids and Liquids
• Because the particles are so much closer in
liquids and solids, there are chances for

particles to attract (or repel). This and the
mass of the particles are main factors in
determining the properties of solids and
liquids.
• Some properties are boiling and melting
points, surface tension, vapor pressure, and
crystalline structure.

Surface Tension
• Surface tension is the
tendency for liquid
surface to contract.
• Depends on attractive
forces
• Compounds that
interfere with the forces
and reduce surface
tension are called
surfactants.

The molecular basis of surface tension.

hydrogen bonding
occurs across the surface
and below the surface
the net vector
for attractive
forces is downward

hydrogen bonding
occurs in three
dimensions

Shape of water or mercury meniscus in glass.

capillarity

stronger
cohesive forces

adhesive forces

H2O

Hg

Solids
• Solids may have a definite structure and are
called crystalline.

• Solids that have no regular shape are called
amorphous.

The hexagonal structure of ice.

The striking beauty of crystalline solids.

The crystal lattice and the unit cell.
lattice point

unit
cell

unit
cell

portion of a 3-D lattice

portion of a 2-D lattice

Phase Changes

Phase Changes

Energy released

sublimination
vaporizing

melting

solid

liquid

freezing
Energy absorbed

gas

condensing